1. Field of the Invention
The present invention relates to a through-type capacitor in which a terminal inserted into and fixed to a dielectric material does not give a large mechanical stress on the dielectric material in case it is thermally expanded due to ambient temperature change.
2. Description of Prior Art
A capacitor, in which a through hole is provided to an almost cylindrical dielectric material in parallel with a cylindrical axis, the internal circumferential side wall surface of the through hole and the external circumferential side wall surface of the dielectric material are respectively metallized to form electrodes, a stepped portion is provided to the external circumferential side wall surface of dielectric material by changing the diameter at the intermediate part of side wall surface, this stepped portion is engaged with and supported by a hole bored to a metal plate for an electrode to form one electrode, a metal conductor is inserted into the through hole and this conductor is soldered to the metallized electrode surface on the internal circumferential side wall surface of the through hole to form the other electrode, is currently used, for example, in the microwave noise preventing filter of a magnetron as the through-type or window type capacitor. In order to alleviate application of a stress due to difference of thermal expansion coefficients of metal and dielectric material resulting from ambient temperature changes to the area between the external surface of a through terminal consisting of a metal conductor to be inserted into the dielectric material and the internal surface of the through hole in the dielectric material of such a through-type capacitor, the inventors of the present invention have filed the methods in the patent application Nos. 62-139735 and 62-157636. According to such methods, it has been proposed that solder resist is partially coated on the circumference of the through terminal inserted into the dielectric material and opposed to the metallized surface of dielectric material in view of avoiding the soldering of the external surface of the through terminal to the entire circumference of internal surface of the through hole in the dielectric material or that a cross section of the dielectric material in engagement with the through terminal is shaped to be rectangular or star-shaped.